To be fair, it wasn't entirely fighting games, they had a Penny Arcade set for instance, targeting fans of the popular video game cartoon satire website, and their unique license Shadowar wasn't based off anything. But yeah, most of the licenses were fighting game licenses and the game had a fighting game style too it, and though it really wasn't as complicated as some people made it out to be, it definitely wasn't yugioh simple. I think the thing that made it seem so complicated was just that it was so different, in a day in age where it seems like half the card games that come out are just a slight revision of some other existing card game (mostly magic the gathering), it really couldn't be compared to anything. Having a reference point always makes it easier to learn a new card game, but it also often has the downside that if a game is say, a lot like magic, that the player your teaching often eventually begins to wonder "why am I not just playing magic?".
That is an interesting side of the issue with the dying CCG genre though, if you make a game too similar to magic, the game dies cause everyone eventually just goes back to playing actual magic, if you make it completely unique, its hard to bring in players cause many people prefer the familiarity of magic, sort of your darned if you do darned if you don't.
It should be noted that UFS came out and became big well before the resurgence of the fighting game genre (aka SF4s release). Street Fighter 4 and even Soul Calibur 4 both came out pretty much after the game was already on its death bed, so the game thrived early on more due to its game mechanics then on popularity of its licenses, probably why it lasted as long as it did.
On the subject of LCG to alteil comparison, EX packs basically gives you 2 rares, 3 commons for 4 dollars. Thats about 5 rares, 12 cards total, for 10 dollars compared to the LCGs 10 rares, 40 cards total for 10 dollars, and the only reason LCG cards are as expensive as they are is do to the ever increasing cost of printing cards, a cost alteil does not actually have. So ex packs don't compare very favorably to the LCG cost to content ratio, but that shouldn't really come as any big surprise. But the style is pretty similar so it does seem to explain why the ex packs are so popular with a lot of players even in spite of their price gouging. Really does make you wonder how much, if any, extra players and sales alteil might have if their ex packs were permanent and priced like LCG packs.
The bunnies of Lavato have special abilities, like 'Action Skill: Make Carrot Disappear.'